Predicting transition from selective withdrawal to entrainment in two fluid stratified systems

TL;DR

This study develops and validates an analytical model to predict the critical submergence depth at which selective withdrawal transitions to entrainment in stratified fluid systems, relevant for environmental safety in oil transfer.

Contribution

The paper introduces a new Weber number-based analytical model validated with high Reynolds number experiments for predicting flow transition in stratified fluids.

Findings

The model accurately predicts the transition point between selective withdrawal and entrainment.

Experimental data confirms the linear relationship between Weber number and critical submergence depth.

The approach provides a robust tool for environmental safety in fluid transfer operations.

Abstract

Selective withdrawal is a desired phenomenon in transferring oil from large caverns in US Strategic petroleum reserve, because entrainment of oil at the time during withdrawal poses a risk of contaminating the environment. In order to predict a critical submergence depth at a critical flow rate, a selective withdrawal experiment at a high Reynolds Number was conducted. A tube was positioned through a liquid-liquid interface that draws the lower liquid upwards. Analysis of the normal stress balance across the interface produced a Weber number, utilizing dynamic pressure scaling, that predicted the transition to entrainment. An inviscid flow analysis, using Bernoulli's principle, assuming an ellipsoidal control volume surface for the iso-velocity profile produced a linear relationship between the Weber number and the scaled critical submergence depth. The analytical model was validated using the experimental data resulting in a robust model for predicting transition from selective withdrawal to entrainment.